[codex] add public contact payments

[ben-kaufman]

Description

Adds public Paykit payments to contacts on Android, matching the iOS public payments flow and the Paykit endpoint identifier spec.

• Publishes and removes spec-compliant Paykit payment endpoints for the current wallet.
• Adds payment discovery and launch flows for Add Contact and Contact Detail.
• Adds contact-tagged activity support and a contact activity screen.
• Threads contact context through immediate and pending send flows.
• Adds duplicate-contact validation parity and repo-level Paykit tests.
• Updates Paykit and bitkit-core bindings for the required endpoint and contact APIs.

Preview

N/A

QA Notes

Suggested reviewer checks:

• On the first-time Pay Contacts screen, choose enabled and continue; verify public endpoints are published for the current pubky.
• On a fresh first-time Pay Contacts path, choose disabled and continue; verify no public endpoints are published.
• Pay a saved contact with public endpoints from Add Contact and Contact Detail.
• Verify sent/pending contact payments attach activity to the contact.
• Verify Contact Activity shows Sent to {name} / Received from {name} titles.
• Paste or scan a pubky and verify routing to profile, existing contact, or add contact as appropriate.

[piotr-iohk]

Tested roughly against this plan. After some time my issue with ln payment disappeared - so in the end I was able to send lightning to contact - still may be worth looking into it. Have some more testing notes below, but mostly that's polishing. Tested against staging.

Areas tested and 🟢 for me.

• send/receive with imported pubky to saved/unsaved contact (onchain and lightning)
• send/receive with created pubky to saved/unsaved contact (onchain and lightning)
• RBF sent tx to concat
• CPFP on received tx from contact
• enable/disable payments with contacts

Some testing notes / observations:

• adding/paying contact via paste invoice glitch - add contact screen "in bg":

Screen.Recording.2026-05-05.at.12.16.38.mov

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• Enter manually is not supporting pubky (since we have it supported on paste/qr code scan etc. - then Send -> Enter manually should also support it)

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• RBF-ed transaction not shown in profile activity (Instead there is a sent tx with Removed from Mempol note)
  • to reproduce:
  • send to contact and RBF transaction
  • see transactions in contact activity

[ovitrif]

LGTM

Didn't encounter any other issue except for the ones that Piotr mentioned, and the pay to iOS not working in that exceptional case when actually the issue was on the iOS side. Once I 'restored' my profile on iOS, paying to the contact via Android worked.

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PS. Recording of how send 2 contact via Send → Paste behaves (issue reported by Piotr):
https://github.com/user-attachments/assets/2fa3a110-a80c-47b2-861a-65f173252684

[piotr-iohk]

LGTM, remaining obesrvations can be addressed separately, issue for tracking: #931

[ovitrif]

re-approved after child PR got merged:

• #930

[chatgpt-codex-connector]

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[ovitrif]

Merging this to master 🎉 🚀 .

Thanks team 🙋🏻